The combustion of hydrocarbon fuels involves the chemical combination of oxygen with the carbon and with the hydrogen, producing water vapor and oxides of carbon. The nitrogen content of the air will frequently enter into the reaction to form various oxides of nitrogen as pollutants. Incomplete combustion can be expected to produce percentages of carbon monoxide, rather than exclusively carbon dioxide, primarily as a result of the impossibility of assuring a perfect mixture of the fuel and air, and the optimum combustion temperature. The classic assumption has always been that the oxygen would have a preference for the hydrogen in cases of incomplete combustion, and this would result in certain percentages of carbon monoxide in the exhaust gases, even where the theoretically quantity of air for proper combustion was present. This gas is not only an undesirable pollutant, but represents a loss of a considerable quantity of the available heat in the fuel.
It has been recognized for at least 50 years that the presence of moisture in the combustion space will significantly modify the combustion process. the injection of water spray into the cylinders of high-output air craft engines has been used as a means of supressing detonation, by the absorption of the heat of vaporization, which would otherwise peak to a point at which the fuel charge would detonate, rather than burn at a uniform rate. Another phenomenon, which has been less well recognized, has been the effects of minute quantities of water vapor in the combustion air. It has been known that the performance of internal combustion engines was frequently improved under conditions of increased humidity. It has also been observed that it was much more difficult to ignite a hydrocarbon fuel-air mixture at all under conditions of extremely low humidity. It was suspected that the water vapor was somehow entering into the combustion process and modifying it, but the nature of this interaction has not been general knowledge. It has, however, been known to specialists in this field for many years. One would normally expect that any dissociation of water vapor into its component oxygen and hydrogen would simply be a passive reaction, as it should re-combine to restore the energy of dissociation. The actual reaction involved, however, is far different. At a particular temperature level related to selected conditions of pressure, the dissociation of the water vapor into oxygen and hydrogen leaves these components in the nascent state, which places them in this condition in the company of the oxygen and hydrogen of the fuel in essentially the same state. Under these conditions, the usual valence laws establishing a preference of the carbon for hydrogen are reversed, with the oxygen then exhibiting a preference for the carbon. The carbon is then completely burned, and the remaining hydrogen is subsequently burned very easily after the oxidation of the carbon, whenever sufficient oxygen is present. This rather surprising behavior has also been observed for many years in a totally different setting. Firemen are very much aware that a coal pile burning from spontaneous combustion cannot be quenched by turning a hose on it. Such a procedure simply results in the migration of enough water vapor into the interior to enter into the dissociation phenomenon, resulting in very efficient burning of all the carbon, and then the subsequent burning of the hydrogen nearer the surface of the coal pile.
The dissociation phenomenon has been incorporated in internal combustion engines and in various forms of heatgenerating devices, frequently without a specific understanding of what was happening. The intake manifold of internal combustion engines provided with carburetors has frequently been supplied with vapor injectors of one form or another, as shown in the U.S. Pat. Nos. 3,724,429; 3,790,139; and 3,107,657. The Wentworth, Jr. U.S. Pat. No. 3,862,819 shows an example of the application of this principle to boilers and furnaces. In this patent, the disclosed system involves a bypass of the air of the primary combustion blower such that a reduced pressure in a container of water induces an inflow of air through a conduit extending to a point below water level. The resulting moisture-ladened air bubbling up through the liquid is removed by the blower, and is intermixed with the main stream of the intake air. Arrangements have also been proposed and used involving a continuous recirculation of the major portion of the air bubbling up through the liquid, which may conceivably increase the vapor content of the resulting air. The recirculation, however, complicates the problem of controlling the amount of vapor actually delivered to the combustion chamber. The quantities of water vapor that are administered to the combustion system in this manner must necessarily be very minute. Excessive moistur will tend to supress the combustion temperature, and interfere with the combustion process rather than improve it. It appears that the amount of water vapor should be closely related to the combustion conditions in a particular installation, so that the degree of incompleteness of combustion in the absence of water vapor can be compensated for by appropriate adjustment of the vapor-injection equipment.